Flash memory is a common type of non-volatile semiconductor memory device. Non-volatile refers to the trait of retaining stored data when power is turned off. Because Flash memory is non-volatile, it is commonly used in power conscious applications, such as in battery powered cellular phones, personal digital assistants (PDAs), and in portable mass storage devices such as memory sticks.
Flash memory devices typically include multiple individual components formed on or within a substrate. Such devices often comprise a high density section and a low density section. For example, a Flash memory may include one or more high density core regions and a low density peripheral portion formed on a single substrate. The high density core regions typically include arrays of individually addressable, substantially identical floating-gate type memory cells. The low density peripheral portion may include input/output (I/O) circuitry, circuitry for selectively addressing the individual cells (such as decoders for connecting the source, gate and drain of selected cells to predetermined voltages or impedances to effect designated operations of the cell such as programming, reading or erasing), and voltage regulation and supply circuitry.
In one particular type of Flash memory architecture, called NOR Flash memory, memory cells within the core portion are coupled together in a circuit configuration in which each memory cell has a drain, a source, and a stacked gate. In operation, memory cells in the core portion may be addressed by circuitry in the peripheral portion to perform functions such as reading, erasing, and programming of the memory cells.
When programming NOR-type Flash memory cells, multiple memory cells may be programmed at once. In a programming operation, each cell being programmed is a load to the power generation circuitry in the memory device. In such a programming architecture, it is desirable to efficiently use power during programming.